Against the backdrop of global warming and exhaustion of fossil resources, production of chemical products using renewable resources, along with production of biofuels, is recognized as an emerging industry, biorefinery, which is an important means for realizing a low-carbon society, and has attracted keen attention.
However, production of biophenol using renewable resources is less productive as compared to production of lactic acid or ethanol because the metabolic reaction from a raw material saccharide consists of a great many steps. In addition, for the reasons that produced phenol inhibits bacterial proliferation and that phenol is cytotoxic, industrial production of phenol has been considered to be impossible.
Important use of phenol is phenol resins. A phenol resin, which is produced by addition condensation of phenol and aldehyde, is one of the oldest plastics, and with its properties including excellent heat resistance and durability, is used for various purposes, such as an alternative automotive material to metal, a semiconductor seal material, and a circuit board even today. Due to extremely high reactivity of phenol and aldehyde as raw materials and to the complicated three-dimensional network structure of resulting phenol resin polymers, precise structural designing and development into nanomaterials thereof had been considered difficult and so had been application to high-value-added use. However, in recent years, the theory of physical-properties of polymers and the simulation thereof have rapidly developed, and therefore it has gradually become possible to create highly functional materials from phenol resins by refining the network structure. Under the circumstances, the phenol resin production in Japan is also increasing year by year.
The currently employed industrial production process of phenol (cumene process) is a typical energy-consumptive process in the chemical industry using petroleum-derived benzene and propylene as raw materials, and requiring great amounts of solvent and thermal energy. Therefore, in the light of global environment conservation and greenhouse gas reduction, there is an urgent need to develop an environment-conscious, energy saving process that allows production of phenol from renewable resources and can reduce carbon dioxide emissions and waste products, that is, to establish biophenol production technologies.
No phenol-producing bacteria in nature have been reported so far.
Examples of known phenol producing technologies using recombinant bacteria include Non Patent Literature 1. In the process of Non Patent Literature 1, a strain constructed by transferring a tpl gene which is derived from Pantoea agglomerans and encodes tyrosine phenol-lyase into a solvent-resistant strain Pseudomonas putida S12, and a strain constructed by transferring an aroF-1 gene which is derived from a Pseudomonas putida S12 strain and encodes DAHP (3-deoxy-D-arabino-heptulosonate 7-phosphate) synthase into a Pseudomonas putida S12 strain were created and used. In addition, from among strains constructed by transferring an aroF-1 gene which is derived from Pseudomonas putida S12 strain and encodes DAHP synthase into Pseudomonas putida S12 strains, strains resistant to m-fluoro-DL-phenylalanine, which is an analogue of phenylalanine or tyrosine, were selected and used. Further, from among the selected strains, strains resistant to m-fluoro-L-tyrosine were selected and used. These strains were subjected to a fed-batch culture under aerobic conditions using glucose as an only carbon source for phenol production in the disclosed technology.
However, the process of Non Patent Literature 1 does not have a practically sufficient phenol productivity.